Commissioning, Handover Documentation, and Post-Installation Service Discipline for Battery Storage Installers

Battery storage installation in the UK is no longer a niche job type. MCS-certified home battery installs climbed 130% in the first half of 2025, reaching approximately 20,000 systems, and the grid-scale market added more than 4 GWh of new capacity in the same year - a 45% year-on-year rise - bringing total operational capacity to around 12.9 GWh. For installers who have grown their battery business alongside solar PV, those numbers represent a significant shift in workload and in operational risk. The back half of a battery job - commissioning, handover, DNO notification, and the warranty period that follows - is where the compliance and commercial exposure sits. This resource covers the four operational disciplines that determine whether a battery storage business stays compliant, gets paid cleanly, and manages warranty calls without losing margin.

Commissioning Validation: What You Must Test Before You Leave Site

Battery storage commissioning is not the same as switching a system on and checking the display reads correctly. A battery energy storage system integrates a battery management system (BMS), an inverter (or hybrid inverter on a solar-paired install), protection devices, and the consumer unit - all of which need to be tested as a system before handover. Getting any element wrong creates compliance exposure that does not go away.

There are four subsystems to validate before you can sign off a commissioning record.

The battery management system needs to show correct cell balancing, temperature monitoring within operating limits, and state-of-charge reporting aligned to the inverter display. The inverter commissioning record - usually a manufacturer-specific document, not a generic certificate - captures the firmware version, grid connection parameters, and the results of protection relay testing. Do not leave site without a signed and dated copy in the job file. Most manufacturers require this record to be retained for warranty claims: if the inverter fails at 18 months and there is no commissioning record, the warranty claim starts with the installer explaining where their documentation is.

The residual current protection on the battery circuit must be matched to the inverter topology. A Type AC RCD on an inverter circuit specified for Type A or Type B is a non-compliance under BS 7671 and the IET Code of Practice for Electrical Energy Storage Systems. It will not prevent the system running day-to-day, but it will produce a finding on any subsequent EICR and puts the installer's certification at risk. Read the inverter datasheet before specifying protection devices, not after commissioning.

Surge protection is now the default expectation for any installation with on-site generation or storage. A Type 2 SPD at the origin protects the inverter - typically a significant piece of sensitive power electronics - from transient voltage events that can destroy it in microseconds. Fitting the SPD at commissioning costs around £100 installed. Not fitting it and replacing an inverter two years into the warranty period costs significantly more, and the failure will look unrelated to the battery install until someone checks whether an SPD was present.

Fire-safe siting must be confirmed at commissioning, not assumed from the survey note. The IET Code of Practice sets a clear preference order: an external weatherproof enclosure on a non-combustible wall, then an integrated garage or outbuilding, then a utility or plant room with appropriate fire-rated separation. A battery installed in a bedroom, on a primary escape route, or against an unprotected timber-frame wall is a non-compliance - and increasingly, one that insurance underwriters check at claim time.

Handover Documentation: What a Compliant Pack Contains

A compliant battery storage handover pack has six components. All six need to be present before a job can be invoiced as complete. Missing any one of them creates a compliance gap that the homeowner will eventually discover - at insurance claim, at conveyancing, or when a buyer's solicitor runs their standard renewables check.

The Electrical Installation Certificate is the primary electrical compliance document. It covers the final circuit, consumer unit modifications, protection devices, earthing and bonding, and any other notifiable electrical work associated with the battery install. It must be issued by a registered electrician under a competent person scheme: NICEIC, NAPIT, ECA, or Stroma. Where the MCS-certified solar or battery firm has its own in-house registration, the certificate sits with the same firm. Where the electrical scope is handled by a separate contractor, both documents need to reach the homeowner in the same handover pack.

The MCS certificate must be issued within 10 working days of installation completion under MCS scheme requirements. On an MCS-registered install - required where the customer intends to register for the Smart Export Guarantee or to meet insurer or mortgage lender requirements - the certificate is issued by the installer through the MCS portal. Check the certificate has been issued and include a copy in the handover pack before closing the job.

The inverter commissioning record is the third document and the one most often missing. Unlike the EIC and MCS certificate, there is no external issuing body chasing the installer for it. It falls to the installer's own process to capture it at commissioning and file it.

DNO notification confirmation is the fourth document. Every battery storage installation must be notified to the relevant distribution network operator. The form of notification depends on system size: G98 is connect-and-notify, meaning the installer can energise the system and notify the DNO afterwards; G99 covers larger installations or combined generation-and-storage setups above the G98 thresholds and requires prior written approval from the DNO before energising. The handover pack should include a copy of the G98 or G99 notification or approval. Systems that have been running for months with nothing on file at the DNO are non-compliant, are not eligible for SEG, and create problems at property sale.

A labelled wiring diagram and emergency procedure are the fifth and sixth documents. The battery must carry a clearly labelled, easily accessible isolation means at the unit itself - not only at the consumer unit. The consumer unit must carry a warning label indicating that on-site generation and storage is present. The homeowner needs a written emergency procedure: who to call, how to isolate the system, what not to do in a fault or fire. These are requirements under the IET Code of Practice, not optional courtesies.

DNO Notification Discipline: Managing G98 and G99 Across a Volume of Jobs

G98 and G99 are the two notification routes that govern how a battery storage installation is communicated to the distribution network operator. The split matters operationally because the routes have different timing requirements and different consequences for getting them wrong.

G98 applies to single-phase devices up to 16 A per phase, which covers the majority of domestic battery installations. Under G98, the installer can energise the system and then notify the DNO after the fact - in practice within 28 days of energising. Most DNOs provide an online portal for this. The notification includes inverter rating, battery rating, and the details of any existing solar PV or other generation on the installation.

G99 applies to larger installations, three-phase systems, or combined generation-and-storage combinations that exceed the G98 thresholds. G99 requires the installer to apply for DNO approval before energising. Approval timelines vary by DNO and by grid capacity in the relevant area: some applications process in two to four weeks; others, particularly in areas with constrained network capacity, can take significantly longer. Building G99 timelines into the project programme at survey stage - not at commissioning - is the discipline that prevents a completed installation sitting disconnected while an application works through the DNO process.

For installers running a pipeline of 10 to 30 active jobs at any time, the DNO notification backlog is one of the more common compliance gaps. Individual notifications are straightforward. Tracking which jobs have been notified, which are pending G99 approval, and which are overdue creates an operational overhead that does not fit naturally into an email-based workflow. A job management system that records notification status against each installation provides the visibility needed to manage this at volume.

Warranty and Post-Installation Service Management

Battery storage warranties run in two separate streams that installers need to manage independently: the workmanship warranty they provide themselves, and the manufacturer warranty covering the battery and inverter hardware.

On MCS-registered installs, the MCS Consumer Code requires a minimum workmanship warranty on every installation, covering the quality of the installer's own work - fitting, cabling, protection devices, earthing, labelling - not the equipment itself. Most installers who are building a renewable energy business carry this warranty as a standard term in their customer contract. What is less common is a documented process for handling workmanship warranty calls at volume: who logs the call, who attends, what scope of remedial work is covered, and how the remedial visit is closed and documented.

Manufacturer warranties are the installer's secondary exposure. Battery cells are typically rated for approximately 6,000 charge cycles, with manufacturer warranties commonly running for 10 years and capacity retention at the end of the warranty period typically specified at 70-80% of the original rated capacity. In practice, a customer on a daily cycling profile may begin to notice performance differences in year seven or eight while the battery is still within warranty. Inverter warranties tend to be shorter, with extended warranty programmes available from most major manufacturers.

The operational challenge is that warranty claims arrive unevenly and often at a lag from the install base. A business that installed 30 batteries in 2023 and 80 in 2024 will start receiving warranty calls from the 2023 cohort in years two through four - precisely when the installer is also scaling new install volume. Having a service record attached to each job, capturing the commissioning date, equipment serial numbers, warranty expiry dates, and any post-installation site visits, is what makes warranty claims manageable rather than reactive.

Post-installation service contracts are increasingly the route by which battery storage businesses convert one-off installs into recurring revenue. A typical service contract covers an annual health check - battery capacity test, BMS diagnostics, inverter parameter review, visual inspection of cables and connections - plus priority response to fault calls. The commercial model is straightforward: recurring annual or multi-year contracts against the growing install base provide predictable revenue that offsets the margin variability in the new-install pipeline.

Managing Battery Storage Operations in Zigaflow

For battery storage businesses managing 15 or more active installations at any time, the operational gap is not finding the work - it is maintaining compliant documentation across the install base and converting that install base into a service revenue stream.

Zigaflow's jobs feature captures the full installation lifecycle in a single record: survey notes, G98 or G99 notification status, commissioning documents, handover checklist, and equipment serial numbers against each job. When a warranty call arrives, the engineer can pull the commissioning date, inverter model, and serial number from the job record without searching email threads or shared drives.

The project tracking feature gives a contracts manager visibility of where every active job sits against the commissioning and handover milestones - including which jobs have outstanding DNO notifications. The invoices feature ties invoice issuance to job completion, which means the six-document handover checklist becomes a gate before the final invoice rather than an afterthought.

For the service contract side of the business, recurring service visits can be set up as separate jobs linked to the original installation, with the previous job's equipment record available as reference. This is the structure that makes a growing battery service portfolio manageable at the volume the installation side of the business generates.

Building a Battery Storage Business That Scales on Compliance

The UK battery storage market is growing fast enough that the operational disciplines that are optional at 20 installs a year become critical at 80. The commissioning record gap that went unnoticed on a quiet week becomes a warranty dispute on a busy one. The handover documentation that the customer did not chase on a small domestic job becomes the evidence needed at insurance claim.

The businesses building a durable battery storage operation treat commissioning, handover, and service management as a defined process - not a checklist done once and then improvised. Set the documentation standard at survey, capture it at commissioning, deliver it at handover, and retain it in the job record. That is the operational discipline that distinguishes a battery storage business that scales from one that gets slower the more work it wins.